Browsing by Subject "stable isotope"

Now showing 1 - 6 of 6
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    Amino Acid Pool Sizes, Turnover, and Kinetics in Spirodela polyrhyza Grown Under Photoautotrophic, Mixotrophic, and Heterotrophic Conditions
    (2018-05) Evans, Erin
    In this study I describe a [15N] stable isotopic labeling study of amino acids in Spirodela polyrhiza (common duckweed) grown under three light and carbon input conditions to mimic photoautotrophic, mixotrophic, and heterotrophic metabolic inputs. Labeling patterns, pool sizes, and kinetics/turnover rates were estimated for fifteen of the proteinogenic amino acids. Estimates of these parameters followed several trends. First, most amino acids showed plateaus in labeling patterns of less than 100% labeling. Second, total pool sizes appear largest in the heterotrophic condition, whereas active pool sizes appear to be largest in the mixotrophic growth condition. In contrast turnover measurements based on pool size were highest overall in the mixotrophic experiment. K-means clustering analysis also revealed more rapid turnover in the auto/mixotrophic. Emerging insights from other research were also supported, such as the prevalence of alternate pathways for serine metabolism in non-photosynthetic cells. These data provide extensive novel information on amino acid pool size and kinetics in S. polyrhiza and can serve as groundwork for future metabolic studies.
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    Analysis of Proteome-scale Protein Turnover in Arabidopsis thaliana Seedlings and Its Application to the Plant Heat Stress Response
    (2015-08) Fan, Kai-Ting
    Protein turnover, the balance between protein synthesis and degradation, is an important aspect of the regulation of cellular processes for organisms as they respond to developmental or environmental cues. How proteome turnover will be influenced in plants when exposed to abiotic stress, especially moderately high temperature, has not been studied systematically. The study of protein turnover in plants, contrary to that of rapidly growing unicellular organismal cultures, is made more complicated by the high degree of amino acid recycling, which results in significant transient isotope incorporation distributions that must be dealt with computationally for high throughput analysis to be practical. In this study, an algorithm implemented in the statistical programing language R, ProteinTurnover, was developed to calculate protein turnover with transient stable isotope incorporation distributions in a high-throughput automated manner using high resolution mass spectrometry and proteomic analysis of stable isotopically labeled plant material. ProteinTurnover extracts isotopic distribution information for peptides identified by tandem MS from raw MS datasets of either isotopic label dilution or incorporation experiments. Variable isotopic distributions were modeled by maximum likelihood estimation using binomial or beta-binomial distributions to (1) unlabeled, (2) newly-synthesized (partially-labled) and (3) fully-labeled peptide distributions. The distribution abundance proportions of old to newly synthesized peptide distributions were calculated using quantities derived from the models. Half-lives and turnover rates were calculated by fitting the change in the distribution abundance prorportions over time to a first-order decay function using non-linear regression. Using ProteinTurnover, turnover rates of hundreds of proteins were measured in soluble, organellar, and microsomal fractions of Arabidopsis seedling roots, using isotopic incorporation. In a second study, ProteinTurnover was used to measure changes in proteome turnover in soluble, organelle, and microsomal fraction of Arabidopsis seedling shoots or roots comparing 22°C and 30°C growth conditions. A total of 571 proteins as exhibiting significant changes in turnover rate in response to elevated temperature were identified in Arabidopsis seedling tissues. In general, soluble proteins extracted from root tissue displayed relatively smaller changes in turnover. Proteins involved in photorespiration, protein folding, stress response, secondary metabolism, and redox signaling pathways exhibited the greatest changes in turnover under heat stress.
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    Data and R code for analysis of mercury concentration and food web differences in walleye and yellow perch from Minnesota lakes with and without invasive zebra mussels, 2019 - 2021
    (2023-02-24) Blinick, Naomi S; Ahrenstorff, Tyler D; Bethke, Bethany J; Fleishman, Abram B; Link, Denver; Nelson, Jenna KR; Rantala, Heidi M; Rude, Claire L; Hansen, Gretchen JA; nsblinick@gmail.com; Blinick, Naomi S; University of Minnesota Department of Fisheries, Wildlife, Conservation Biology; Minnesota Department of Natural Resources
    This dataset contains δ13C and δ15N stable isotope data for 3,765 biological samples (fish, littoral macroinvertebrates, and zooplankton) collected from 21 lakes between 2019 and 2021, collaboratively by the University of Minnesota and the Minnesota Department of Natural Resources. In addition, 403 samples have corresponding mercury data, based on laboratory analyses conducted by USGS (Tate et al. 2022).
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    Mercury accumulation in raptors
    (2016-01) Keyel, Edward
    Mercury (Hg) is a toxic heavy metal that when methylated to form methylmercury (MeHg), bioaccumulates in exposed organisms and biomagnifies through food webs. Most studies examining Hg concentrations in birds of prey have focused on species associated with aquatic systems such as Bald Eagle (Haliaeetus leucocephalus). My goal was to assess Hg concentrations in multiple species of migrating raptors in the upper Midwestern US. From 2009-2012, 966 raptors of 11 species were captured at Hawk Ridge, Duluth, MN, USA. Breast feathers were sampled and analyzed for total Hg concentrations, which is a good analog for methlymercury. Mean Hg concentrations ranged from 0.11 – 3.46 ppm. Carbon and nitrogen stable isotope values were analyzed for Sharp-shinned Hawk (Accipiter striatus) and Merlin (Falco columbarius) because they had the highest mean Hg concentrations with 3.46 and 2.15 ppm respectively. Stable isotope analysis suggested that both species consumed terrestrial prey and that total Hg concentration increased with trophic level. Further analysis of Sharp-shinned Hawk and Merlin feather samples show Hg increases with age. The Hg concentrations observed in Sharp-shinned Hawks, Merlins, and Northern Goshawks (Accipiter gentilis) represent a concern when compared with concentrations found in the American Kestrel (Falco sparverius); one of the few raptors with enough experimental data for comparison.
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    The rise and fall of the Ruffe (Gymnocephalus cernua) empire in Lake Superior
    (2017-12) Gutsch, Michelle
    Invasive species are a global problem, impacting property, habitats, ecosystem function, and native species. Our ability to predict future habitat and spread of aquatic invasive species is limited because it is challenging to collect and integrate information regarding life history, movement, and habitat, especially across continents. Ruffe (Gymnocephalus cernua), a demersal, invasive fish, has caused substantial ecological damage. Given the potential for ecological impacts, such as native fish declines, ongoing concern regarding the spread of Ruffe in the Laurentian Great Lakes is warranted. But there are significant research gaps regarding life history, movement, and Ruffe distribution in the native and non-native range. Therefore, the overall goals of my dissertation were to acquire life stage-specific data for Ruffe, including dispersal, seasonal, and spawning movements and characterize their life cycle and to develop a lake-scale species distribution model at 30-m resolution. Regarding the first goal, I found that Ruffe has characteristics that allow them to adapt to a range of environments, including rapid maturation, relatively long life and large size, batch spawning, genotypic and phenotypic plasticity, tolerance to a wide range of environmental conditions, broad diet, and multiple dispersal periods. To address the second goal, I developed a species distribution model for Lake Superior because Ruffe has established in the lake but is not yet widespread. I found that a variety of species distribution models constructed to predict Ruffe suitable habitat based on environmental data resolved to a variety of scales all performed similarly but varied substantially in the area of habitat predicted, particularly the offshore habitat area classified as suitable. I conclude that to interpret the outputs of the Ruffe species distribution models, both model performance and the ecology of Ruffe must be considered to better characterize its fundamental niche. Broadly, I demonstrate the importance of synthesizing the life stage-specific biology and distribution of an invasive species with species distribution models to advance our ability to predict the future habitat of an invasive species.
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    A tunnel speleothem based stable-isotope record of Atlantic Multi-Decadal Oscillation forcing of precipitation in the Midlands, United Kingdom
    (2019-08) Shull, Carolyn
    Cave speleothems are an established source of preserved data used in paleo-environmental reconstruction, as climate and land use information can be recorded in the carbon and oxygen isotopes. Speleothems in the tunnels of the canals in West Midlands, UK were investigated as another potential record as they appear to experience a rapid growth rate, a requirement to detect short-term climate events and low-amplitude climate signals. Formation in artificial structures restrict the potential record to the past 150 years, while other speleothem-based proxies span millennial time scales. Upon analysis, speleothem oxygen isotopes reflect the Atlantic Multi-Decadal Oscillation (AMO), and carbon and oxygen isotopes are correlated to land use changes. The results indicate speleothems from canal tunnels in central England potentially provide a record of land use changes and precipitation source water related to the AMO. Tunnel speleothem isotope data have the potential to serve as valuable datasets in climate teleconnection and modeling studies.